The present invention relates to apparatus for tensioning and fusing plastic material strips, in which overlapping strip sections can be inserted between a pair of clamping members and by movement of one clamping member relative to the other the strip is tightened and subsequently fused by frictional heat. Tightening and fusing apparatuses of this kind are known (for example in U.S. Pat. No. 3,669,799) in which one clamping member is formed as a roller. This roller may be driven gradually in one direction for tightening the strip and, after such tightening, is rotated in an oscillatory reciprocating manner during which the strips are fused or welded together by frictional heat. In this known apparatus the clamping pressure has to be produced between the tensioning roller and a backing jaw by pressing the roller against one of the strips located between it and the backing jaw and this compressive pressure then remains constant. Operation of the apparatus is therefore fairly strenuous. Moreover, a relatively cumbersome gearing is required to convert the initial gradual stepping movement of the roller for tightening the strip to the oscillatory movement of the roller for fusing the strips together.
Tightening and fusing apparatuses are also known in which a tightening roller is continuously driven via a reduction gear for tightening the strip and in which reciprocating movement is produced for fusing the strip by a separate gearing. This tightening and fusing device requires a fairly costly reduction gear and also a separate drive for a reciprocating movement.